Benthamia spiralis A.Rich.

Hervouet, Jean-Michel, Descourvières, Pascal, Hermans, Johan & Longou, Ludivine, 2025, Revision of the genus Benthamia A. Rich. (Orchidaceae, Orchidioideae, Habenariinae), Adansonia (3) 47 (11), pp. 171-249 : 234-235

Benthamia spiralis A.Rich.

Monographie des Orchidées des Îles de France et Bourbon: 39 ( Richard 1828). — Habenaria dissimulata Schltr., Beihefte zum Botanischen Centralblatt 33: 404 ( Schlechter 1915). — Benthamia spiralis var. dissimulata (Schltr.) H.Perrier , Bulletin de la Société botanique de France 81: 34 ( Perrier 1934).

TYPE MATERIAL. — Mauritius • sine loc.; J. Néraud 8; holotype: P [ P00738316 ] !.

ETYMOLOGY. — From the Latin “ spiralis ”, spiral, referring to the arrangement of the rachis.

PHENOLOGY. — Mainly May to October, but flowering time rarely noted on specimens.

DISTRIBUTION AND ECOLOGY. — Mauritius. Habitat unknown, except the vicinity of a marsh mentioned for one specimen ( Fig. 89 ). CONSERVATION. — This species is at least Critically Endangered (CR), with an area of occupancy severely fragmented and less than 10 km ² and an inferred continuing decline (criterion B2ab). The most recent collection, by Francis Friedmann, dates back to 1971, there is thus no recent proof that it is not extinct.

ADDITIONAL SPECIMENS EXAMINED. — Mauritius • sine loc.; J. B. G. M. Bory R43052 ; W ! • sine loc.; L. H. Boivin s.n.; P [ P00738422 ] ! • sine loc.; L. H. Boivin s.n.; P [ P00738537 ! plant in the middle only] • sine loc. • L. H. Boivin s.n.; P [ P00738421 ] ! • sine loc.; L. H. Boivin s.n.; P [ P00738538 ] ! • sine loc.; 1831; L. Bouton s.n.; P [ P00738527 ] ! • sine loc.; 1846-1848; L. H. Boivin s.n.; W ! • Marais contigu au chemin de Chirac près du point le plus élevé; X.1849; L. H. Boivin s.n.; P [ P00738389 ] ! • sine loc.; VIII.1862; P. B. Ayres s.n.; P [ P00738413 plant in the middle only] ! • Pétrin; 20°24’31”S, 57°28’19”E; V.1971; F. Friedman 1162; P [ P00738417 , P02088511 ] !.

NOTES

When Achille Richard described this species in 1828, it was for him clearly distinct from Satyrium spirale Thouars. The latter species appears on page 21 of the same publication un- der the name Habenaria spiralis (Thouars) A.Rich. Moreover , he wrote on the Néraud 8 type specimen: « non in P. Th. », meaning that it was not a Du Petit-Thouars species. The name was validly published since no one had used the name Benthamia spiralis before. When Schlechter wanted to transfer Benthamia spiralis A.Rich. to Habenaria in 1915, he was hindered by the already existing Habenaria spiralis (Thouars) A.Rich. which has Satyrium spirale Thouars as basionym. He therefore created a new name: Habenaria dissimulata Schltr. Many subsequent authors have mistakenly considered Benthamia spiralis A.Rich as a new name for Satyrium spirale Thouars. To add to the confusion the original Thouars name Satyrium spirale was illegitimate because it was already used by Swartz in 1788, for what is now Spiranthes torta (Thunb.) Garay & H.R.Sweet from Central America. For this reason, Lindley applied the new name Spiranthes africana in 1824, later changed to Benthamia africana (Lindl.) Hermans in 2014. Examination of the types proves them to be different, we have thus Benthamia spiralis A. Rich , endemic to Mauritius, as a different species from Benthamia africana , from Madagascar and the Mascarenes. That Benthamia spiralis A.Rich. was a different species or variety was also the interpretation of Perrier de la Bâthie who wrote ( Perrier 1934: 33): « on doit le distinguer comme variété et certains botanistes pourraient même le considérer comme une espèce distincte » (« it must be considered as a distinct variety and some botanists could even consider it as a distinct species »), « avec un port plus robuste et des feuilles plus grandes, plus larges et plus nombreuses » (« with a more robust habit, larger, wider and more numerous leaves »), but he mistakenly named it Benthamia spiralis (Thouars) A.Rich. var. dissimulata (Schltr.) H.Perrier and among other specimens he cited one from La Réunion island (Boivin 1064, P[P00738525]!, which is for us merely Benthamia africana .

This species differs from Benthamia africana mainly by the more numerous cauline regularly alternate linear leaves, borne up to the base of the rachis, and also by the longer lateral lobes of the lip, the petals with fleshy tips and revolute margins, and the much longer floral bracts, up to twice the length of the ovary. Both plants are growing together and field observations are necessary to know to which extent they hybridize.

DESCRIPTION

Erect terrestrial herb 42-66 cm tall. Tubers 2, fusiform, 4 × 0.8 cm, roots 2-6, up to 6 cm long, 1-2 mm in diameter. Stem with the base covered by 1-2 sheaths, 3-5 mm in diameter. Leaves 5-10, erect, linear or strap-like, alternate subdistichous, acute and glabrous, 8-19 cm × 4-11 mm, regularly spaced (internode 2-3 cm), up to the rachis. Rachis terminal (4)7-17(23) cm, bearing 27-45 flowers roughly arranged in a spiral, 4-6 mm apart. Floral bracts linear-lanceolate, acute, enveloping the ovary at the basis, 8-15 mm long, up to twice the length of the ovary. Ovary fusiform, twisted, glabrous, slightly curved at the apex, almost vertical, 5-8 mm long. Flowers resupinate, 2.5-4.5 mm long, green; sepals 1-veined; dorsal sepal elliptic-oblong, 2-3 × 0.8-1 mm; lateral sepals similar or slightly longer, 2.1-3 × 0.9-1 mm; petals oblong-triangular, thickened at the apex, with slightly revolute margins, 2.2-2.6 × 0.8-1.2 mm; lip 2-3 × 1.2 mm, concave in the proximal part, subcanaliculate, clearly trilobed at apex, like a trident, with a thickened midlobe 0.5-1 mm long, obtuse, lateral lobes acute, 0.3-0.5 mm long; spur 0.8-1 mm, slightly bilobed, slightly contracted at the base. Column subterete, 0.5-1 × 0.8-1 mm, with an obtuse to subacute nose-shaped apiculus 0.2-0.3 mm long, with lateral broadly rectangular auricles, with irregular margins; rostellum trilobed, hardly visible in dried material.

Figures

FIG. 89. — Distribution map of Benthamia spiralis A.Rich.